1. Field of the Invention
The present invention relates to heat exchangers and, in particular, to heat exchangers with removable tubesheets and tube bundles for use in applications involving high temperatures and rapidly changing thermal gradients.
2. Description of the Related Art
A variety of heat exchangers are used in the electric power generation and chemical manufacturing industries. Generally, such heat exchangers comprise a shell, a plurality of tubes (i.e., a tube bundle), a tubesheet, and a head. In operation, steam may be routed through the shell and water may be routed through the tubes. The opposite is also possible. As they pass through the heat exchanger, the steam is cooled and the water is heated.
Heat exchangers employed in the chemical manufacturing industry may be subjected to extremely high temperatures and rapidly changing thermal gradients. For example, the temperature in a heat exchanger employed in a hydro-desulphurization process may go from a normal operating range of about 600-1000 degrees fahrenheit to about 2000 degrees fahrenheit after a hydrogen bubble ignites in the reactor vessel. These elevated temperatures may last as long as three minutes. Such high temperatures and the accompanying thermal gradients may cause thermal stresses that may result in permanent physical deformation and/or cracking of the heat exchanger components.
It is desirable for heat exchangers used in chemical manufacturing applications to withstand high temperatures and rapidly changing thermal gradients without deformation or cracking. In addition, it is desirable for such heat exchangers to permit removal of the tubesheet and the tube bundle for maintenance and/or replacement.
Conventional heat exchangers, however, do not meet these goals. Most conventional heat exchangers do not provide full access to the tubesheet and tube bundle for easy maintenance and/or replacement. Those heat exchangers that do provide for full access to the tubesheet and tube bundle are not designed to withstand the high temperatures encountered in many chemical manufacturing applications.
It is accordingly an object of this invention to overcome the disadvantages and drawbacks of the known art and to provide a heat exchanger with a tubesheet and tube bundle that can be easily removed from the shell for maintenance and/or replacement.
It is a further object of this invention to provide a heat exchanger designed to withstand high temperatures and rapidly changing thermal gradients.
Further objects and advantages of this invention will become apparent from the detailed description of a preferred embodiment which follows.